HORSES

OAHN equine surveillance study on Lyme disease and anaplasmosis – preliminary results  

Luis Arroyo, Scott Weese, Alison Moore, Murray Hazlett

During the summer of 2016, Ontario equine practitioners were asked to participate in the collection of serum from horses in the province. In particular, we requested samples from horses that had never traveled outside of Ontario, were outdoors for more than 6 hours a day, and were more than 2 years of age. Equine veterinarians who agreed to participate submitted a total of 567 samples.

Antibodies against the C6 antigen of Borrelia burgdorferi (IDEXX Snap 4DX Plus test) were detected in 27 (5%) horses; 5 additional horses were positive for Anaplasma spp. antibodies.

Antibodies against OspA, OspC, and/or OspF of B burgdorferi (Cornell University equine multiplex ELISA), were identified in 39 (7%) samples.

This information was presented at the annual meeting of the Ontario Association of Equine Practitioners in February 2017. Further analysis is ongoing.   AHL

Alcohol and Gaming Commission of Ontario (AGCO) Death Registry:  2003 - 2016 postmortem summary

The Alcohol and Gaming Commission of Ontario (AGCO; formerly the Ontario Racing Commission, ORC) continues in its proactive approach to advance racehorse welfare and safety of human and animal participants. In 2003, Ontario became one of the first North American racing jurisdictions to require mandatory reporting of racehorse deaths, in order to monitor, research and improve knowledge of why these events occur. Postmortem (PM) exams conducted at the Animal Health Laboratory through the AGCO Death Registry continue to provide comprehensive data regarding the causes of morbidity and mortality in racehorses in this province. To date, PMs have been carried out on 1,013 horses through the Death Registry program (Table 1). Annual variation in the number of PM cases reflects discretionary requirement for PM on the part of the Registrar of AGCO.

A summary of significant PM findings is provided in Table 2. A comprehensive review of AGCO PM cases was conducted in 2015 as part of a separate retrospective study and as a result, some cases have been reclassified from results presented in previous editions of the AHL Newsletter. Results of the study will be published in the near future in the Journal of Veterinary Diagnostic Investigation.

Since 2015, computed tomography (CT) of fractured and contralateral limbs has been carried out on select Death Registry postmortem cases through collaboration with the Diagnostic Imaging section of the Ontario Veterinary College Health Sciences Center. The goal of this in-depth examination is to identify pre-existing lesions, primarily in bone, that contribute to catastrophic fractures. 

The procedure was continued in 2016, with CT imaging of 24 of 27 (89%) fracture cases submitted for PM exam. Pre-existing lesions in bone or occasionally soft tissue were identified and considered predisposing to fracture in 10 of 24 (42%) cases.

Exercise-associated sudden death is of special concern among those cases reported through the Death Registry (Table 3). Significant pulmonary hemorrhage was identified in 78 of 163 (48%) sudden death cases. The cause of death in such cases is often attributed to exercise-induced pulmonary hemorrhage (EIPH), although the pathogenesis of pulmonary hemorrhage in these horses is not well understood. Severe acute hemorrhage involving pericardium or body cavities was identified in 30 of 163 (18%) sudden death cases. In a significant proportion of exercise-associated sudden death cases, no significant lesions were identified and the cause of death remained undetermined (37 of 163, 23%). It has been speculated that exercise-associated cardiac arrhythmia, leading to acute heart failure and pulmonary hypertension, may be the underlying cause of death among many of these horses, and may also contribute to pulmonary hemorrhage in these animals.¹

Summaries of postmortem submissions to the Animal Health Laboratory under this program and diagnoses by body system for these cases are provided in the following tables.   AHL

Reference

1. Physick-Sheard PW, McGurrin MKJ. Ventricular arrhythmias during race recovery in Standardbred racehorses and associations with autonomic activity. J Vet Intern Med 2010; 24: 1158-1166.

AGCO Death Registry-continued.

Table 1. Breed distribution of AGCO Death Registry submissions to the AHL, 2003-2016.

Table 2. Significant postmortem lesions identified in AGCO Death Registry submissions by body system, 2003-2016.

Table 3. Significant postmortem lesions contributing to or causing death in exercise-associated sudden death cases reported to the AGCO Death Registry, 2003-2016.